The Grand Duchy of Hesse and by Rhine (German:Großherzogtum Hessen und bei Rhein), or the Grand Duchy of Hesse (German:Großherzogtum Hessen) between 1806 and 1816, was an independent country and member state of the German Confederation as of 1806, when the Landgraviate of Hesse-Darmstadt was elevated to a Grand Duchy which it remained until 1918, when the monarchy was overthrown. Hesse lost its independence when it joined the German Empire in 1871. Before 1866, its northern neighbour was its former sister Landgraviate, since 1803 an Electorate, of Hesse-Kassel – for this reason, this state was sometimes colloquially known as Hesse-Darmstadt.

After World War II, the majority of the state combined with Frankfurt am Main, the Waldeck area (Rhine-Province) and the former Prussian province of Hesse-Nassau to form the new state of Hesse. Excluded were the Montabaur district from Hessen-Nassau and that part of Hessen-Darmstadt on the left bank of the Rhine (Rhenish Hesse), which became part of the Rhineland-Palatinate state. (Bad) Wimpfen—an exclave of Hessen-Darmstadt—became part of Baden-Württemberg, in the district of Sinsheim. After a plebiscite on 29 April 1951, Bad Wimpfen was transferred from Sinsheim district to Heilbronn District. This change to Heilbronn was carried out on 1 May 1952.